Marking complicated tempo changes

Sometimes you may wish to indicate tempo changes by showing 2 note
values with an equals sign between them. For simple cases, this is
fairly straightforward, but if you want to include beamed notes or a triplet,
a little more work is required. Another use of this notation is to
show that the music is to be played in "swing time," as in this example,
which has two ordinary eight notes on one side of the equals sign,
and a triplet made up of a quarter and eighth note on the other: